Interesting article, teaser, and surprisingly easy to understand (esp. for me with no formal biochem background). I notice that one of the co-authors is Donald Layman whom Jimmy Moore interviewed here.

This must be one of the studies that Dr Layman refers to in the interview. Googling foods high in leucine, I come up with eggs, chicken, moose, but no beef. It's all coming together for me now. Thanks so much for digging that up - it gives me a clearer idea of how to proceed.